Stable gyro reference for projectiles

ABSTRACT

A stable gyro reference for enabling flight corrections to spinstabilized projectile trajectories. A drive plate on the projectile body engages and supports the gyro during launch to transfer projectile spin to the gyro. After launch, the gyro separates from the drive plate permitting it to spin freely. Because of the mechanical support given by the drive plate to the gyro during the high acceleration launch, various conventional gyros are suitable for use. Control of range and dispersion errors can be effected through the use of such a gyro system in conjunction with suitable aerodynamic or thruster methods.

United States Patent 1191 Bolick Oct. 21, 1975 [54] STABLE GYROREFERENCE FOR 2,386,686 10/1945 l-lunsdorf 244 123 PROJECTILES 2,402,7186/1946 Albree 244/3.l 3,304,029 2/1967 Ludtke 244/32 [75] Inventor: R.Glenn BOllCk, Fred'encksburg,

Primary Examiner-Stephen C. Bentley [73] Assignee: The United States ofAmerica as A istant Ex minerC. T. Jordan represented by the Secretary ofthe Navy, Washington, ABSTRACT [22] Filed: 1973 A stable gyro referencefor enabling flight corrections [21] AppL NOJ 322,803 to spin-stabilizedprojectile trajectories. A drive plate on the projectile body engagesand supports the gyro during launch to transfer projectile spin to thegyro. U-Sn CL 3 After launch the gyro eparates from the drive plate [51]Int. Cl. F42B 15/14 permitting it to Spin f l Because f the mechanicalFleld of Search support given the drive plate to the gyro during the 5R, 541; loz/DIG- 3 high acceleration launch, various conventional gyrosare suitable for use. Control of range and dispersion References Cltederrors can be effected through the use of such a gyro UNITED STATESPATENTS system in conjunction with suitable aerodynamic or 1,181,1365/1916 Hayden 244/31 thruster methodsl,3l6,363 9/1919 Hayden 244/3.l1,459,198 6/1923 Dunajeff 244/3.1 8 1 D'awmg F'gure z/ 1 I9 Ill I6 H l9A; II

i 11 22 GUIDANCE B A CONTROL 7 POWER SYSTEM I SOURCE STABLE GYROREFERENCE FOR PROJECTILES BACKGROUND OF THE INVENTION 1. Field ofInvention This invention relates generally to gyroscopic space sensingand more particularly to a gyroscope arrangement which will provide astable reference for spinstabilized projectiles. Various techniques havebeen evolved in the past to provide control of spinning projectilesduring flight. For example, canards or fins mounted on a despun sectionof the projectile can provide aerodynamic surfaces which control theflight path of the projectile in response to commands from a guidancesystem. Also, virtually straight-lined trajectories have been obtainedby selectively detonating small charges located circumferentially on thebase in response to command signals. Additionally, gas ejection has beenutilized to produce control forces on bodies of revolution in flight.

2. Description of the Prior Art All of the foregoing techniques havebeen used successfully in the past. Each requires a reference or datumby means of which the actual trajectories canbe compared to the desiredtrajectory. Such references have usually taken the form of gyroscopes.These gyroscopes have customarily been provided with their own drive tospin up the gyroscope and have also required extremely ruggedconstruction in order to withstand the high g loads imposed during gunlaunch. U.S. Pat. No. 3,304,029 discloses such a gyro arrangement in aguided missile. US. Pat. No. 3,369,772 illustrates such complex gyroarrangements in a spin-stabilized rocket.

SUMMARY OF THE INVENTION The present invention obviates theaforementioned problems by holding the gyro in contact with the driveplate on the projectile body during launch to transfer the projectilespin to the gyro and spin up the gyro. The setback forces and releasedevices hold the gyro against the drive plate during launch. Thismechanical support eliminates the need for ruggedized bearings and sinceduring part of the time period of interest the projectile body isrotating with almost the same radial velocity as the gyro, the bearingsare less critical than on fixed systems. The gyro is held against thedrive plate by a suitable releasable coupling and this means that noorientation of the gyro is required since it is automatic with the axisof rotation being always aligned with the gun tube at launch.

STATEMENT OF THE OBJECTS OF INVENTION It is a primary object of thisinvention to provide a new and improved stable gyro reference forspinstabilized projectiles.

It is another object of this invention to provide a gyro reference forprojectiles wherein projectile spin is utilized to spin up the gyro andobviate the need for a separate gyro drive.

It is a further object of this invention to provide a stable gyroreference for gun launched projectiles wherein the gyro is mechanicallysupported during the gun launch and thus the need for massive gyrocomponents is precluded.

It is yet another object of this invention to provide a gyro referencewhich possesses indefinite shelf life because no power unit is requiredfor spin up.

It is a still further object to this invention to provide a stable gyroreference for spin-stabilized projectiles in which the gyro spin axiswill be automatically aligned with the gun tube at launch.

BRIEF DESCRIPTION OF THE DRAWING Other objects, advantages and novelfeatures of the invention will become apparent upon consideration of thefollowing detailed description of the invention when considered inconjunction with the accompanying drawing wherein the single FIGURE ofthe drawing illustrates a full section through a fragment of aprojectile body and showing the various components of applicantsinvention in their storage or pre-launch positions.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawing,there can be seen a projectile body 10 provided with an interiorspherical cavity 11. A spherical gyro 12 is disposed within the cavity11. A pair of pins 13 are disposed in aligned apertures in theprojectile body 10 and gyro 12 and serve to hold the gyro firmly againsta drive plate 14 which is formed of a high friction composite material.This is the normal storage position of the gyro 12 with its transverseaxis represented by the line 15.

A plurality of bearings 16 are arranged about the surface of the cavity11 for supporting the gyro 12 when it is rotating. The bearings 16 maybe hot or cold gas, electromagnetic, electrostatic, or any other type ofnon-friction gyro bearings. A bearing power source 18 of the appropriatetype is provided for energizing or powering the bearings 16.

A plurality of sensors 19 are disposed on the surface of the cavity 11and are used to provide flight position data by detecting the relativeorientation of the projectile body 10 and gyro 12 during operation. Theoutput of the sensors 19 is fed into a guidance control system 20 toenable flight corrections when necessary. The guidance control system 20may be any of the systems described above in the background of theinvention or may be any other type suitable for guiding spinstabilizedprojectiles during flight.

OPERATION In order that better understanding of the invention might behad, its mode of operation will now be described. The projectile 10 isloaded into a gun barrel (not shown) with the gyro 12 in contact withthe drive plate 14 and the pins 13 in the positions shown in thedrawing. When the propulsive charge (not shown) is fired, the projectile10 rapidly accelerates (accelerations of 10,000 gs are not uncommon)down the gun barrel, and begins to spin rapidly about the spin axis 21due to the rifling in the gun barrel. The high setback forces hold thegyro 12 firmly against drive plate 14 and thus the spin of theprojectile (normally about 300 RPS) is imparted to the gyro whichlikewise spins around the axis 21. While the projectile body 10 is beingspun up, the pins 13 are retracted'by centrifugal force from the gyro 12into the apertures in the projectile body 10.

When the projectile exits from the gun barrel, the projectile body 10 isno longer accelerating and the bearings 16 then function to shift thegyro along its spin axis until the transverse axis 15 of the gyrocoincides with the transverse axis 22 of the cavity 11. The gyro 12 isnow freely spinning with its spin axis oriented with the longitudinalaxis of the gun barrel. During flight, the relative orientation of theprojectile body and gyro 12 is continuously monitored by the sensors 19and the guidance control system 20. These changes in relativeorientation may be due either to the normal ballistic trajectory of theprojectile 10 or they may be perturbations due to outside sources. Theguidance control system 20 will function to correct the path of theprojectile 10 whenever it tends to deviate from the desired trajectory.

It should be appreciated that the invention may be practiced other thanas specifically described. For example, the drive plate 14 could bereplaced by a serrated surface or other releasable mechanical connectionbetween the projectile body 10 and gyro 12. Also, the setback forcealone could be relied upon to maintain sufficient frictional contactbetween the projectile and gyro to insure spin up of the gyro. Althoughthe gyro 12 has been shown as spherical in configuration, it should beappreciated that conventional gyros of disc configuration would besuitable for use with short range projectiles where the firingtrajectory were relatively flat. And further, the pins 13 could bereplaced by shear pins or any other releasable device which would serveto retain the gyro in contact with the drive plate during the storageand handling and yet release it subsequent to launch. Obviously, manymodifications and variations of the present invention are possible inthe light of the above teachings.

What is claimed is:

l. A stable gyro reference for spin-stabilized projectiles comprising:

a projectile body; I

a gyro disposed within a cavity in said projectile body;

means for releasably coupling said gyro to said pro jectile body duringlaunch whereby the stabilizing spin of the projectile will be impartedto said gyro, said coupling means allowing said gyro to spin freelyfollowing launch;

bearing means on said projectile body for supporting said gyro followingrelease; and

means responsive to the relative orientation of said projectile body andsaid gyro for generating error signals to enable correction of thetrajectory when necessary.

2. The gyro of claim 1 wherein said coupling means comprises pinsdisposed in mating apertures of said projectile body and said gyro andretractable into said projectile body by centrifugal force during spinup to release said gyro.

3. The gyro of claim 2 wherein said coupling means includes a driveplate on said projectile body and engaging said gyro during launch tospin up said gyro.

4. The gyro of claim 3 wherein said drive plate is formed of highfriction composite material.

5. The gyro of claim 3 wherein said drive plate is serrated and engagescorresponding serrations on said gyro.

6. The gyro of claim 1 wherein said bearing means comprise gas bearings.

7. The gyro of claim 1 wherein said bearing means compriseelectromagnetic bearings.

8. The gyro of claim 1 wherein said bearing means comprise electrostaticbearings.

1. A stable gyro reference for spin-stabilized projectiles comprising: aprojectile body; a gyro disposed within a cavity in said projectilebody; means for releasably coupling said gyro to said projectile bodyduring launch whereby the stabilizing spin of the projectile will beimparted to said gyro, said coupling means allowing said gyro to spinfreely following launch; bearing means on said projectile body forsupporting said gyro following release; and means responsive to therelative orientation of said projectile body and said gyro forgenerating error signals to enable correction of the trajectory whennecessary.
 2. The gyro of claim 1 wherein said coupling means comprisespins disposed in mating apertures of said projectile body and said gyroand retractable into said projectile body by centrifugal force duringspin up to release said gyro.
 3. The gyro of claim 2 wherein saidcoupling means includes a drive plate on said projectile body andengaging said gyro during launch to spin up said gyro.
 4. The gyro ofclaim 3 wherein said drive plate is formed of high friction compositematerial.
 5. The gyro of claim 3 wherein said drive plate is serratedand engages corresponding serrations on said gyro.
 6. The gyro of claim1 wherein said bearing means comprise gas bearings.
 7. The gyro of claim1 wherein said bearing means comprise electromagnetic bearings.
 8. Thegyro of claim 1 wherein said bearing means comprise electrostaticbearings.